The present invention relates to a finely-divided powder spray apparatus for discharging finely-divided powders together with a gas stream so that the powders are sprayed onto a member to be sprayed as a substrate.
A spacer spray apparatus is known as a representative example of finely-divided powder spray apparatuses, the apparatus uniformly spraying a prescribed amount of spacers for liquid crystal displays (spacer beads) as the finely-divided powders having a uniform particle size between substrates constituting a liquid crystal display panel for liquid crystal display devices, for example, between a glass substrate and a glass or plastic substrate so that the spacers are formed into a single layer.
In the liquid crystal display panel of a liquid crystal display device and the like, particles (spacer beads such as plastic particles and silica particles) having a uniform particle size of about several microns to several tens of microns are sprayed or coated as spacers as uniformly as possible in an amount of 10 to 2000 particles per unit area of 1 mm2 to form a single layer between substrates, for example, between glass substrates, between plastic (organic glass, etc.) substrates other than the glass substrates, and between the plastic substrate and the glass substrate, (hereinafter the glass substrate will be described as a representative example and the aforementioned member to be sprayed are simply referred to as the glass substrate as a whole) so that the space to charge liquid crystals is formed.
Some conventional spacer spray apparatuses spray spacer particles onto the glass substrate by transporting the fine spacer particles together with a gas flow of air, nitrogen, etc., through a thin pipe (transportation pipe) and discharging the particles from a swinging spray nozzle pipe together with the gas stream. The spacer particles are finely-divided powders having a size of several microns to several tens of microns, and liable to float. They are various types of plastic particles or silica particles, and liable to be charged. Therefore, it is difficult to spray the spacers onto the glass substrate at a prescribed density with excellent repeatability. These apparatuses can charge the spacer particles in accordance with a charged polarity (electrostatic polarity) and ground the glass substrate and a table so as to reliably spray the spacer particles onto the glass substrate at the prescribed density.
Recently, the size of a liquid crystal display panel has been increased gradually and a plurality of liquid crystal display panels have often been made of a single glass substrate. It is therefore required to fix a larger glass substrate on a table disposed in a chamber of the spacer spray apparatus. In general, the glass substrate is fixed onto the table by vacuuming the substrate from the side of the table. However, the density of the spacers deposited at one spot, where the glass substrate is fixed, is different from the densities at other spots depending on a strength of vacuuming the glass substrate, i.e., the spacers cannot be uniformly sprayed. Further, if a difference in electric field strengths generates on the surface on the glass substrate, the spacers cannot be uniformly sprayed out in some cases.
An object of the present invention is to provide a finely-divided powder spray apparatus which can adjust a density of finely-divided powders such as spacers for liquid crystal displays to be sprayed onto a member such as a glass substrate.
The finely-divided powder spray apparatus of the present invention having a spray nozzle pipe for discharging the finely-divided powders from the tip together with a gas stream, which is disposed at a prescribed distance from a member to be sprayed, and comprising:
a moving-speed control factor entry means which enters moving-speed control factors for controlling a moving-speed of the spray nozzle pipe in a prescribed area of the surface of the member to be sprayed; and
a moving-speed control means which controls the moving-speed of the spray nozzle pipe in the prescribed area of the surface of the member to be sprayed, based on the control factor entered by the moving-speed factor entry means.
In the finely-divided powder spray apparatus of the present invention, the moving-speed control factor entry means is provided to enter the moving-speed control factor for each prescribed area on the surface of the member to be sprayed and the moving-speed control means is provided to control the moving-speed of the tip of the spray nozzle pipe depending on the area of a spray point, at which the finely-divided powders are sprayed, based on the control factor entered for the prescribed area.
According to the finely-divided powder spray apparatus of the present invention, the moving-speed factor is entered by the moving-speed control factor entry means for each prescribed area of the member to be sprayed. Based on the result of a test spray, for example, the moving-speed control factor for decreasing the moving-speed of the tip of the spray nozzle pipe is entered for the prescribed area having a lower density of finely-divided powders deposited, whereas a moving-speed control factor for increasing the moving-speed of the tip of the spray nozzle pipe is entered for the prescribed area having a higher density of finely-divided powders deposited. Further, the moving-speed control means controls the moving-speed of the tip of the spray nozzle pipe based on the moving-speed control factor entered by the moving-speed factor entry means, and thus the moving-speed of the tip of the spray nozzle pipe can be controlled in the prescribed area on the surface of the member to be sprayed in order to achieve a uniform density over the whole surface of the member to be sprayed.